A recent improvement in the LED emission efficiency has led to the replacement of lamps and fluorescent lights with LEDs as the light sources of various lighting systems. This is attributable to many features of LEDs, including their compact sizes, capability to emit multicolored beams, ease of control and low power consumption. In the lighting application requiring a high optical output, however, the optical output of a single LED is still insufficient. As a result, a plurality of LEDs are arranged for use as a lighting system.
In the case of LCD displays, for example, a lighting system is used as the backlight thereof having a plurality of packages of LEDs emitting red, green and blue beams arranged on a metal core printed circuit board, as described in [Non-Patent Document 1]. Further, as described in [Patent Document 1], a plurality of white LED packages are arranged on a flexible printed board and used in combination with a light-guiding plate or other means for use as the backlight.
[Patent Document 1]
Japanese Patent Application Laid-Open Publication No. 2002-16262
[Non-Patent Document 1]
SID03 Digest, pp. 1262-1265 (2003)